means an API declared as such, either in
a component.xml file, or by virtue of having a "@since" tag in the
JavaDoc. Technically, an API should be both in the component.xml file,
and have a @since tag, but if only one of those conditions is true,
we assume the omission is the error.

Provisional API

means a non-API that was documented
as, basically, "we'd like this to be API someday, but have not had the
time or resources or experience to officially declare it as such". The
significance being, that anyone who uses it is accepting the risk of having to
adjust to future changes (whereas APIs never change).

Internal non-API

is the case where some adopter has used some
class clearly designated as "internal". While we still will use care to not
capriciously break adopters who do that, its less clear we could accommodate, but we will work to figure out why
they were, if there is a better way, etc.